Questions: Which type of enzyme inhibitor decreases affinity for binding the substrate? Answers A - D A uncompetitive B none of the above C noncompetitive D competitive

The answer is D: competitive.

Explanation for each option:

A. Uncompetitive: Uncompetitive inhibitors bind only to the enzyme-substrate complex, not to the free enzyme. This type of inhibition actually increases the enzyme's affinity for the substrate because it locks the substrate in place.

B. None of the above: This option is incorrect because there is a correct answer among the given choices.

C. Noncompetitive: Noncompetitive inhibitors bind to an enzyme at a site other than the active site, which does not affect the binding affinity of the enzyme for the substrate. Instead, it decreases the overall rate of the reaction.

D. Competitive: Competitive inhibitors bind to the active site of the enzyme, directly competing with the substrate. This type of inhibition decreases the enzyme's affinity for the substrate because the inhibitor and the substrate compete for the same binding site.

Summary: The type of enzyme inhibitor that decreases affinity for binding the substrate is a competitive inhibitor.